Abrading apparatus



Dec. 5, 1944. w, KEEFER 2,364,077

' ABRADING APPARATUS Filed Oct. 25, 1941 3 Sheets-Sheet l Dec. 5, 1944. w L K EPER 2,364,077

ABRADING APPARATUS Filed Oct. 25, 1941 5 Sheets-Sheet .2

wull'er L.

,Omafldwn & WLZZ Gamma/: 5

Dec. 5, 1944. w. L. KEEFER ABRADING APPARATUS Filed 001;; 25, 1941 3 Sheets-Sheet 5 mzlrz. Keger.

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Patented Dec. 5, 1944 ABItADI NG APPARATUS h Walter L Keefen, Hagerstown, Md; assignor to Bangborn; Corporation; Hagerstown, Md, a corporation 61*Maryland u u n 1 Application octoberl 25, 1941, Serial No. 416,577

is cl i s. (o1'. 51 'f9 This invention relates to abradingapparatus;

and moreparticularlytoacentrifugalwheel for projecting abrasive, such as steel gri-t and shot, at an abrading velocity upori w'orkpieces to be cleaned. j it t Machines of the type-herein deseribed marbe said to consist of three main parts, namely;

rotor having one or more abrasiverlpropel'ling blades, an abrasive supplyl means, and a-transf'er.

mechanism which functions to transfer the abrae rnent and repair, the several parts of the 'wheelbeing readily adjustab'letolvary thefdirection of discharge :of abrasive from the wheel. Further objects and advantages of this invention will appear from the following description and claims takenjin connectionlwiththe append: 'eddrawingswherein 3 n 1: 1 ij "Figure liis a front elevation ofa centrifugal abrading- Wheel embodying the present invention,

taken on the line [-3-]; QfEIFigJZythe housing bee ing omitted.

blades, of the rotor in suchmannera that the abrasive is dischargedonto th -inner endsofi the blades eta predetermined pointyor zone the abrasive subsequentlybeingitdischarged? from the ends of the blades in a predetermined Z0118.-

In providing an. improved centrifugarwheel roithrowing abrasive; it i is all major {object 1 of this invention to providea'noveltransfer means'which is designed to receivefabrasive from suitabletabra' sive feed: means, the abrasive :being. transferred almost simultaneously to theinnerendsoI the: throwing blades ofzthe rotor. y i a p v A further object "of thisxinventioririststhe prcn vision of a novel transfermeans: arranged torreceive abrasive from a feed means and itransfer it immediately onto the inner endsiof theublades of the rotor at a predetermined point or zone with aminimumof dispersion. i

Still a further object of this. inventionlisthe provision of a novel transient mechanism for a centrifugal wheel whereinthe abrasivelied bytthe feed means is transferreduat a maximum velocity onto the inner ends of u the throwingwbladesi at a predetermined point; or zone; the, transfersoccnra ring at substantially the point of feedrzwhereby; the l abrasive is in contact withthe transferrmech anism for only a. very short. period of' time; and

Fig'nZ isa section taken on the lineJ Z-QZR of Fig. l with portions of the front and 'rear walls of the. housing shown in section; and the feed spoutshownin outline, the feed sp'outnot being visible in" a truesection taken on the linerZ-e-Z because oflits offsetwith respect to a vertical linerthrou'gh the from Fig.4.i M1 i i n n i Fig; 3 isan exploded view of the severaluparts of the wheel of Figs. 1 and 2 incsideelevation.

Fig. dis: a front elevationofrthe feedspout of the-wheel of Figs. 1 and 2 shown in combination center of the wheel, as evident i with portions of. the holder, the spout being 1 wheel of Figs. LandZ.

shown in the positionfiit fdownblastwheel.

would occupy, in a 'Fig; 5 is a rear elevationw of t the lower part of the feed spout ofFig. 4. n

Fig. 6 is a front elevation of the holder for i the guard and feed spoutl of the wheel. 1: in

FigJl is a perspective of theuimpeller of the Fig. 8- is awfront; elevation of l the guard of the Wheel. it i i Fig. 9 is an elevation of a portion of nthe guardp oi Fig. 8 looking in the direction indicated by the friction; and consequently the power required to i drive; the mechanismis reduced 170 a.- minimum:

A further object of this inventionris the: pro.- v

vision of novel transfer andbfeed meehanism wherein a chamber eccentricor atrone'isideof the axis of therotor is-provided to receive theuabraa sive in combination :with means operatiteuin the chamber to transferwtherabrasive almost simula taneously and at asubstantial:velocityvonto the inner ends of theuthrowing blades oi: "thalrotorg the discharge being in a direction to enable the;

abrasive to be picked up therebywithjaminimum ofimpact i arrow 9. n 1 n n in Fig. 10 is a. rearelevationlof the guard of Fig. 8. 1;1is an elevation of a portionof theguard of Fig." 10 lookinginsthef direction indicated by the arrow H.

Referring; to; Figsl l and the centrifugal abrasiveithrowing wheel'there illustrated include-s three: main elements; namely, a rotorlR, an abra;

siven feed meansiF; and artransfermechanism T.

- The: wheeli is preferably surrounded by a housingvhaving end walls (not shown); and'iront and rear walls I0 and 12. Preferably wear plates l3,

as showniniFig. 2, are provided on theinterior Still a further'obiect i ofthisinventiomisthe provision of a centrifugal:throwing;wheelioirnovel pl i: on lone: life; andiieasilyr accessibleiior:repiak:e+

construction wherein'the parts arez-relativiely sime n of thehousing walls tcpreventmdamagethereto n The rotor It comprises a flangeM" mountedon a; rotatableushaftmlu, driven by any suitable means such as an. electric. motor (not shown): flanger lx lnhas atcenteringz flange I5 thereon and n a relatively heavy disc I6 having radial grooves therein to receive and support a series of channelshaped blades l'l, said blades being preferably sharpened at their inner ends, as shown in Fig. 1 at l8, to facilitate their cutting through the abrasive stream from the transfer mechanism. For a detailed description of such rotors and the manner of securing the blades thereto, attention is directed to Patent No. 2,108,211, issued on February 5, 1938.

The abrasive feed means F includes a feed spout l9 arranged to receive abrasive fed by gravity, as from an elevated hopper, and conduct the abrasive to the transfer mechanism T. Spout I9 is provided with a flange 2| at its upper end' for attachment to a suitable support and a flange 22 at its lower end. The lower end of the spout is adapted to enter an aperture 23 formed in a holder 24 (Figs. 3and 4). Flange 22 (Fig. 4) is engaged by a clamp 25 secured by a bolt 26 passi'ng -through a threaded hole in holder 24, this arrangement 'serving'to hold the lower end of the feed spout inits'proper position. As flange 22 and aperturer23' are: circular, the feed spout can be 'fittedin the'holderregardless of the clock dial position of aperture 23. relative to the center of the holder. The discharge opening 2150f feed spout 19 (Fig. is bounded by a shield or trough 28 for approximately 180, the shield being of diameter to fit within an aperture 29 in a guard member 3|. Shield 28 functions tomaintain the discharge opening of the feed spout centered in aperture 29. In the assembled position, shield 28 preferably'extends to the inner edge'of bevel 29 of apof the "mechanism for'abrasive. Ordinarily, as

the stream of abrasive discharged by the feed spout is cut into wads by the impeller blades,

there is some ricochet of the abrasive which tends to block the discharge endof the feed spout. This 'ricocheting'is kept to a minimum by a current of air induced through opening 31' by the rotation of the impeller" and-blades l1, this current of air flowing Ov'er'the top of abrasive passing through'thefeed spout. This current of air catches the abrasive particles that would otherwiseblock the'feed spout and carries them back into the impeller, which accomplishes their discharge.

The holder 24 is of generally circular shape and provided with a cylindrical section 32 arranged to. fit within an opening 33 in wall l0 and the attached wear plate I3. A flange 34 is provided on holder 24 to fit against-a ring 35 preferably welded to the inside of wall 10, as indicated at 36,

and held thereagainst by suitable means,,such as clamps, whereby the holder may be rotated to position aperture 23 and the feed spout secured therein in different positions about the axis of the rotor. Such clamps are disclosed in my copending application Serial No. 324,860, filed March 19,

number and size 'ofthe shims, the position of guard member 3| within the central portion of the wheel can be adjusted axially of the assembly.

The guard member 3| comprises a disc 38 secured to holder 24 by bolts countersunk in the disc at 39 and passing through holes 4| in the holder. Disc 38 is formed with aperture 29 which receives shield 28 so that the abrasive passes from the discharge opening of the feed spout into the interior of the wheel in a generally uninterrupted stream.

The disc 38 isformed with a peripheral flange 42 and a central boss 43 which serve to seat the 'a curved surface or groove 46 is provided curving outwardly tothe face of the disc. The degree of curvature of this groove is indicated by the lines A, B, and C of Fig. 9, which are taken on the arcs A, B,1and C of Fig. 8, respectively.

, The groove -46 functions to receive some of the batted abrasive as the vanes of the impeller 'cut through the stream of abrasive. It has been found that the edges of the blades interrupt some abrasive and push it back against disc 38. As this abrasive has 'someiforward velocity, it travels along the groovev 46 and returns to the impeller vanes; 'In the absenceof such' a groove, it has been found that suflicient abrasivetwill accumulate in a short time to block the feed spout an appreciable amount;

The groove 46 terminates at a ridge or rib 41 (Fig. 10). i From ridge 41 to the periphery of the disc, the:disc surface is formed with a series of relatively, deep grooves 48, extending normally from ridge 4'! to, the periphery; of the disc. Grooves '48 function to collect stra "particles of abrasive traveling between the impeller vanes and disc '38,. and transfer them into the path of the rotor blades adjacent the discharge point of the main stream from the impeller; Otherwise, it has been found that a large percentage of these particleswill continue to travel around the face of disc 38anddischarge at other than the desired zone.

A- portion of 'the outer periphery of the guard disc section. which includes aperture 29 and groove 46, is bounded by an 'arcuate shaped flange or guard 49. which extends from a point adjacent the ridge 41 to the far edge of aperture 29, or'through an arc of about The outer end of guard 491is preferably provided with an inwardly extending'flange 5|, 'so.that the inner surface of the guard is formed in the shape of a channel. l

1 An outwardly projecting hollow cylindrical boss 52 is provided at the center of the guard disc 38 opposite boss 43, boss 52 being closed at its outer end at 53 and formed with a slot 54 facing aperture '29. Slot 54 preferably extends throughabout An aperture 55 is provided. in disc 38 in line withthe hollow section of boss 52 and an opening 56'1'formed in the center of holder 24. As shown inFig. *2.,'this arrangement provides for an unrestrictedac'cess of air to slot 54, which aids in the scribed;

An annular groove 51 in the face of disc 38 is provided about the outer periphery of boss 52 for a purpose to be later described.

The impeller orfltransfer mechanism proper shown" iriFigs. 1, 2, 3;, and 7 at 58 includes a hollow cylindrical; section '59 having an enlarged abrasive. i i i i i In operation, abrasive is fed through feed spout portion Gal on the end-:thereotarrangedktobe fits. ted'withinra centrallrecess 6% formed in disc Hi and against centering 'fiange. IS; the impeller being secured inpositionby a bolt 63. (Fig. 2). entering flange 14 so that the pellerrotates stream, so that thesresultant feeder abrasive onto the inner ends of blades I1 will be substantially atoneipoint. l

withrotor R. Preferably bolt 63 passes through anfinterna'l boss 64 formed, in thecenter of sec-J tion 59. To insure the impeller .58 being always assembled in the same relative position with disc I6, 3.18101; 651scuti in theperiphery of section 6| to fit over thehead of a bolt 66 which is secured indisc l4. i N

The left face of section 59 as viewed in Figs.

series ofv'anes68 and BS" secured thereto, each vane extending in a substantially radial direction with its inner endsspaced sufiiciently from the center toclear the outer periphery of boss 52 inoperation. I i i i l i *Vanes 68 and 69 are preferably arranged al-; ternately around the impeller, there being four vanes of each type on the' illustrated embodiment, making a total of ight vanes. It is pre ferred to havethe samenumber of vanes on the impeller asblades Won the rotor, and toposi tion-the impeller sothateachimpeller vane leads itscorresponding rotor blade by approximately 15, measuring from the centerlines of the vane and. the blade. This position of theimpeller is insured;by slot 65andbolt 56. i

Each of vanes -68 progressively 1 increases in width from its inner end to'itsouter end, the latter being defined. by an edge 1| substantially parallel tothe face. of wall 61. A flange 12 is provided along the outer edge of each vane 68 extending upwardly 1mm the abrasive contact-- ing face l3to confine the abrasive to the throw} ing face of the vane and prevent its escape therefromnW Each of vanes 59 has its Widest sectionjadja cent the center of theimpeller, the narrowest sectionbeing at the outer periphery of the impeller. Thus vanes 68 and B9 taper in opposite directions. Each vane 69 has its inner and widestend defined byan edge 14 parallel to edges "H of vanesBB, and is also provided with a flange 15 serving the same purpose as flange 12..

. Eachvane 69 is formed on its inner end adjacent the hollow center defined by th inner ends of the vanes with an axially extending gen 1 By reason of the rotation of the impeller and. i

the rotor blades, an appreciablecurrent of air is induced through Opening 54 in-boss 52 of the guard member. This. air current has been found to prevent any' downward leaking of stray abrae sive. This air current also, as well as the airin-::

duced through opening 3 l in the feed spout, aids in preventing blocking of the feed spout. e The impeller with its alternately tapered vanes has been found to actually increase the capacity ofthe transfer mechanism for abrasive as com.-

pared with an impeller having non-tapered blades, or having all .bladestaperin one directiony' Thiscan only be explained at this timefby the fact'thatjwith blades of alternate tapers, there is less tendency to push abrasive back into the feedspout and block or choke the spout. in The described structureis of particular advantage in that theyabrasive fed inte -the transfer mechanism travels-therethrough only a relatively short period of time; and is almost simultaneous= l-y discharged therefrom. This resultsin a mini, mum expenditure of power as distinguished from adevice employing a' circumferential cage where:

in the abrasive is; carried around .and around in the cage, andresults in a minimum of wear *be-; cause of the relatively short time the abrasive is in contact with theltransfer mechanism. 3

In actual tests, it hasbeenfound that the her-c indescribed mechanism abrades or cleans work:

ni s morewun f y t an icr Wh ls.

i a he t a the res ingd s rint o and dra erally wedge-shapedlug 16 which, as shown in a the assembly of Fig. 2,-fitswithin annular groove 51 of the guard with a running clearance. When the wheel is operating, lugs'lfi cooperate with groove 51 to form [9 andjidischarged through opening 21 ina direction substantially normal to the plane of rotation of impeller 58, the latter rotating with rotor R. As the abrasive is discharged in a sub.- stantially continuous stream, it encounters vanes 68 and 69 which divide it into a series of separate wads or charges. Y

The abrasive charges are given a velocity in the direction of movement of the impeller vanes, and are discharged fromthe zonein which the impeller operates at apoint adjacent the end of guard 49onto theinner ends of blades H, the di rection of discharge and the speed of'the par ticles being such thatthe abrasive is'picked up by blades I! with a minimum of impact.

The guard 49, groove 46,and grooves 48 funcftion to return the strayparticles of abrasive to the impeller vanes or the path of the main a seal against the escape of penin om r sih twc se ics vanes mounted n s- A imo ifi i n and chang which W with n h meaningud rang c equivalency th c m a e' h fior intended to b inc uded 1 Iclaim; l i I 1. In an abrading apparatus, a rotor having a p u a i of a r si e p o ell ng blades, he i t ends. of ale b ad s e ng s ac apa t o d fine a central opening, im eller in. said central t t t ab it t e axis f sai r t r the an of ne e s i g t per d i a d rc t gn t g i'ige r p h v n gre e id h t; it O er? and than at itsihner end, the vanes of the other seri l e ta ed a d re on to pr d a ane having a greater width at its inner end than at its. outer end, and means to feed abrasive over e s de fid es o said a es- 2. An abrasive feed and transfermechanism iorusewith a centrifugal. abrading rotor com- 3 prising an abrasive feed spout a disc-like mem- .ber surrounding the discharge end of said'feed shout, and a rotatable impeller "secured te'said rotor to intercept the abrasive discharged from the discharge end of said feed spout, said disclike member being formed with a plurality of grooves thereinadjacent the impeller extending in: a direction substantially parallel to the direc tion of discharge of abrasive by said impeller.

r 3. An abrasive feed and transfer mechanism for use with a centrifugal abrading rotor, comprising an abrasive feed spout having its discharge end eccentric of the axis of said rotor, a member having a substantially fiat surface surrounding =the discharge end of said feed spout and facing in the direction of discharge from said spout, and means to intercept the abrasive discharged from said feed spout and-discharge it in a direction substantially parallel to the flat surface of said member, said surface being formed with a plurality of grooves extending in-a direction substantially parallel to the direction of the abrasive discharged by said last mentioned means.

v4. An abrasive, feed and transfer mechanism for use with a centrifugal abrading rotor comprising an abrasive feed spout having its discharge end eccentric of the axis of said rotor, a member having a substantially flat surface surrounding the discharge end of said feed spout and facing in the direction of discharge from said spout, and means to intercept the abrasive discharged from said feed spout and discharge it in a direction substantially parallel to the flat surface of said member, said surface being formed with a relatively large groove beginning adjacent said feed spout and decreasing in depth to a point spaced from said/feed spout in the direction of movement of said abrasive;

5. A transfer mechanism for use with a centrifugal abrading rotor comprising an impeller having two series of vanes mounted to rotate about the axis of said rotor, the vanes of one series being tapered in a direction to provide a vane having a greater width at its outer end than at its inner end, the vanes of the other series being tapered in a direction to provide a vane having a greater width' at its inner end than at its outer end, the vanes of the two series being alternately arranged.

6. An abrasive feed and transfer mechanism for use with a centrifugal abrading rotor comprising, a boss substantially aligned with the axis of said rotor, a rotatable impeller including a plurality of vanes arranged around and adapted to revolve about said boss, means for feeding a stream ofabrasive over lateral edges of said vanes at a position offset from said boss, and said boss having a passage therein terminating in a slot of limited peripheral extent for directing a current. of air across the abrasive stream.

'7. An abrasive feed and transfer mechanism for transferring abrasive onto the propeller blades of a centrifugal rotor comprising, a plurality of impeller vanes rotatable with said rotor and extending inwardly short of the axis of the rotor to define a centralspace, a disc at one end of the impeller vanes, a boss carried by said disc extending into said central space, said disc having an aperture therein radially displaced from the axis of the rotor, means for suppling abrasive through said aperture over edges of the impeller vanes, and said boss and said disc having a passage therein terminating in a slot in the boss of limited peripheral extent for directing a current of air across said aperture.

8,-An abrasive feed and transfer mechanism for transferring abrasive onto the propeller blades of a centrifugal rotor comprising, a plurality of impeller vanes rotatable with said rotor andextending inwardly short of the axis of the rotor to outline a central space, closure means at one end of the impeller vanes, a boss carried byTsaid-closuremeans extending'into said central space, said closure means having 3.1131381? ture therein radiallydisplaced from the axis of the rotor, afeed spout for:supplying;abrasive through said aperture over edges of the impeller vanes, said boss and, said closure means, havinga passage therein terminating in a slot in the boss of limited peripheral extentfordirecting a current ofair across said aperture, and theupper side of said feed spout having-an opening therein adjacent said closure means;

9. An abrasive transfer mechanism for trans-,

ferring' abrasive onto the inner; ends of propeller blades at a predetermined point ,in the rotation thereof comprising, an impeller including 'a plurality'of vanes extending inwardly short of the axis,1of;the impeller to define a central space, a disc at oneend of the impellervanes, a hollow boss extending from the disc into said central space; said disc having an aperture ally of said aperture. 7 a

10. A mechanism for transferring abrasiveonto the inner ends of propelling blades of centrifugal abrading-apparatus comprising, a rotatable impeller including a plurality of vanes, a stationary disc mounted adjacent one end of saidimpeller vanes, said disc having an apertureextending therethrough at a point offset -from-the-axis-of saidimpeller, ,-means for supplying abrasive through said aperture and over the edges of said vanes, the face of said disc adjacent said vanes having an arcuate groove therein extending-from said aperture and decreasing in depth in the direction of rotation of said impeller vanes.

11. A mechanism for transferring abrasive onto the inner ends-of propelling blades of centrifugal abrading apparatus comprising, a rotatable im= peller including a plurality of vanes,,a stationary disc mounted adjacent one end of said-impeller vanes, said disc having an aperture extending therethrough ata point offset from the axis of I said impeller, means for supplying abrasive through said aperture'and over the edges of-said vanes, the face of said disc adjacent said vanes having: a groove therein extending from said aperture-and decreasing in depth in the direction of rotation of said impeller vanesto a point circumferentially spaced from said aperture, and

said disc havingaplurality'ofsubstantially parallel grooves therein extending in a chordal direction from the end of the first groove to the periphery of said disc. r

12. A mechanism for transferring abrasive onto the inner ends of propelling blades of centrifugal abrading apparatus comprising, a rotatable impeller including a plurality of radial vanes, a stationary disc mounted adjacent one end of said impeller vanes, said disc havin an aperture extending therethrough at a point offset from the axis of said; impeller, means for supplying abra- .sive through said aperture and over the edges of to a point circumferentially spaced from said aperture, and an arcuate shaped guard extending along the periphery of said disc a suflicient distance totembrace said aperture and said groove.

13. Amechanism for transferringabrasive onto the inner ends of propelling blades of centrifugal abrading apparatus comprising, a rotatable impeller including a plurality of radial vanes, a stationary disc mounted adjacent one end of said impeller vanes, said disc havingan aperture extending therethrough at a point offset from the 1y short of the axis of the rotor, an impeller rotatable with said rotor-and arranged between i the inner ends of said propeller blades, said imaxis of said impeller, means for supplying abra sive through said aperture and over the edges of said vanes, the face of said disc adjacent said vanes having a groove therein extending from said aperture and decreasing in depth in the direction of rotation of said impeller vanes to a point oircumferentially spaced from said aperture, said disc having a plurality of substantially i parallel grooves therein extending in a chordal direction from the endof the firstjgroove to the periphery of the disc, an arcuate shaped guard extending along the periphery, of said disc a suflicient distance to embrace said aperture and peller including an end wall and a pluralityof radially arranged vanes extending laterally from said end wall terminating in free edges within planes defined by the edges of said propeller blades, a stationary arcuate shaped guard hav ing a circumferential length of approximately one-third the circumference of the impeller mounted between a path described by the inner ends of said propeller blades and a path describedby the outer ends of said impeller vanes, and a feed spout terminating adjacent the free edgesof said impeller vanes within a sector definedby the ends of said guard and at a position radially displaced from ,the axis of the, impeller for supplying a stream of abrasive axially over the, free edges of the impeller vanes iwhereby said groove, said disc having a passage therethrough substantially aligned with the axis of said impeller, and means associated with said passage for directing air drawn through said passage towards said aperture.

i 14. Amechanism for transferring abrasive onto the propeller blades of a centrifugal rotor come prising, an impeller mounted for rotation about the axis of the rotor including a cylindrical secl l tion anda radial wall with two series of vanes carried by and extending laterally from saidwall,

the free edges of the vanes of one series tapering in one direction and the free edges of the vanes of the other series tapering in an opposite direcsive over the free edges of said vanes.

plurality of propeller blades terminating inwardly short of the axis of the rotor, an impeller rotatable with said rotor arranged between the inner ends of said propeller blades including a plurality of radially arranged vanes having free lateral edges, a stationary arcuate shaped guard having I a circumferential length of less than one-half the circumference of theimpeller mounted between the path described by the inner ends of saidl propeller bladesiand the path described by the outer ends of said impeller vanes, and a feed spout terminating adjacent the free lateral edges of said impeller vanes having a discharge opening in the terminal end located within a sector defined by the circumferential ends of said guard and at a position radially displaced from the axis of the impeller for supplying abrasive axially over the free lateral edges of the impeller vanesand onto outer end portions of the impeller vanes whereby theabrasive is discharged from the impeller vanes adjacent an end of said guard. 16. In abradingapparatus, a rotor including a plurality of propellerblades terminating inwardthe abrasive issuing from the feed spout is supplied to outer end portions of the impeller vanes as they pass one end of theguard and the abrasive, is discharged from the impeller vanes as they pass the other end of said guard.

17." Amechanism for transferring abrasive onto Q the inner ends of propeller blades of centrifugal abrading apparatus comprising, a rotatable im peller including a plurality of radial vanes having free lateral edges, normally stationary adjustable said aperture and axially over the free lateral I edges of said vanes, an arcuate shaped guard car 1 means covering the free edges of said vanes sai'd means having an aperture extending there-' throughat a pointiofiset from the axis of the impeller, means for supplying abrasive through i riedby said means adjacentsaid aperture emtion, a flange carried by and following the free edge of each vane, and means for feeding. abra- 15. In abrading apparatus, a rotor including a bracing the periphery of said impeller for a distance, of approximately degrees, and said aperture having a radial extent less than the radius of the impeller and a circumferential ex-f tent less than the circumferential length of said 18. A'mecl'ianism for transferrin abrasive onto the inner ends of propeller blades of centrifugal abrading apparatus comprising, a rotatable impeller including a plurality of substantially radial vanes having free lateral edges, normally stationary adjustable means covering the free edges of said vanes, said means having an aperture extending therethrough at a point offset from the axis of the impellenmeans for supplying abrasive through said aperture and axially over the free lateral edges of said vanes, an arcuate shaped guard carried by said means extending circumferentially over the periphery of the impeller and terminating in an edgepositioned less than degrees forwardly of said aperture mea sured in the direction of rotation of said impeller, and said aperture having all radial dimensions thereof less than the radius of the impeller and a circumferential extent less than the arcuate length of said guard. a

WALTER. L. KEEFER. 

